The present invention relates to storage systems, and more particularly, to techniques for optimizing storage system performance.
In modern storage systems, power dissipation is a crucial issue that affects manufacturing costs and reliability. For example, a device that consumes a significant amount of power produces more heat, which requires temperature control devices such as cooling fans, etc. These added devices add to the costs. With regard to reliability, hard disk drives fail more frequently at high operating temperatures. One solution that reduces power dissipation is for a hard disk drive to enter a power saving mode when the hard disk drive is not being accessed by the host system. A hard disk drive typically waits to determine whether there is any activity from the host system. If there is no activity for a certain amount of time, the hard disk drive may then enter a power saving mode. A problem with this solution is that the wait time can be significantly long.
Another problem with this solution is that during a power saving mode, if the hard disk drive receives an input/output (IO) command, the hard disk drive needs to exit the power saving mode, which takes some time. Similarly, if the hard disk drive receives an IO command while the hard disk drive is performing a maintenance operation, it may be difficult or impossible to abort the operation. After exiting the power saving mode or aborting a given maintenance operation, the hard disk drive can then perform the requested task, but with some delay. The delay can be problematic in audio-video (AV) streaming or real-time applications, where additional unexpected command latency may compromise real-time performance.